JP4232278B2 - Hydrodynamic bearing and spindle motor equipped with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates mainly to a brushless motor (hereinafter abbreviated as a motor) used in a magnetic disk drive, and more particularly to a dynamic pressure bearing structure thereof.
[0002]
[Prior art]
In recent years, with high capacity, high speed, high precision, and low noise of HDD equipment in the OA field, high precision is strongly demanded for a motor that drives a magnetic disk. In a bearing structure provided between the stator and the stator, it has been studied to adopt a dynamic pressure bearing.
[0003]
For example, as disclosed in Japanese Patent Application Laid-Open No. 11-55898, the dynamic pressure bearing has a shaft supporting a rotor inserted in a sleeve fixed to the stator, and the sleeve is interposed between the sleeve and the shaft. Is filled with lubricating oil. The radial load supports the rotor load using the dynamic pressure generated when the motor is driven by the dynamic pressure generating groove provided in the sleeve. On the other hand, the load in the thrust direction supports the load in the thrust direction of the rotor by the point contact between the thrust plate and the shaft end SR surface by the pivot bearing structure.
[0004]
FIG. 6 shows an example of a conventional dynamic pressure bearing. A shaft 51 attached to a motor rotor (not shown) is inserted into a sleeve 52 fixed to a stator (not shown). A thrust plate 53 is provided on the sleeve 52, and a dynamic pressure generating groove 54a is provided on the side surface of the shaft 51 or the inner peripheral surface of the sleeve 52 facing the shaft 51. Further, a lubricant 55 is filled in a gap between the shaft 51, the sleeve 52, and the thrust plate 53. An annular recess 57 is provided on the surface of the sleeve 52 facing the thrust plate 53.
[0005]
By configuring the dynamic pressure bearing in this way, the radial load supports the load using the pressure generated in the dynamic pressure generating groove 54a generated by rotating the rotor when the motor is driven, and the load in the thrust direction is The load is supported by making point contact with the thrust plate 53 on the SR surface of the shaft end.
[0006]
[Problems to be solved by the invention]
However, if the annular recess 57 is provided on the surface of the sleeve 52 that faces the thrust plate 53, when the shaft 51 is inserted into the sleeve 52 in the process of assembling the hydrodynamic bearing portion, air is caught in the lubricating oil 55 and the recess 57. There is a risk that air bubbles 56 are present in the air. When the air bubbles 56 are interposed in the bearing portion, the air bubbles 56 enter the dynamic pressure generating groove 54a due to the flow of the lubricating oil 55 in the bearing when the motor is driven. There is a problem that it becomes smaller, the bearing rigidity in the radial direction is insufficient and the load cannot be supported, and the swing of the rotating body increases.
[0007]
Further, when the bubbles 56 bite into the SR surface of the shaft end portion constituting the thrust bearing portion, the point where the shaft 51 and the thrust plate 53 are in point contact causes oil shortage and the thrust bearing portion is seized. Insufficient lubricating oil 55 that absorbs heat generated from the contact portion has caused problems such as accelerated thermal deterioration of the lubricating oil 55.
[0008]
Japanese Patent Application Laid-Open No. 7-75313 discloses a method for discharging bubbles when bubbles are mixed inside the hydrodynamic bearing. The example is cited in FIG.
[0009]
This is provided with a gas vent hole 68 in which the recess 67 and the other end surface of the sleeve 62 communicate with each other, and the air that is bitten inside the bearing when the shaft 61 is inserted into the sleeve 62 is passed through the gas vent hole 68. Through the bearing.
[0010]
However, this is configured so that the gas vent hole 68 is passed through the sleeve 62. When machining the sleeve 62, a lathe is usually used. In order to allow the gas vent hole 68 to penetrate the sleeve 62, simultaneous drilling on a lathe results in drilling with a drill. However, when the drill used for drilling becomes longer than the diameter, the drill itself The drill was damaged during machining due to insufficient rigidity. Accordingly, there has been a problem that it is difficult to increase the axial length of the sleeve 62, that is, to increase the bearing length of the hydrodynamic bearing.
[0011]
Further, when simultaneous drilling on the lathe is stopped and fine drilling is performed by electric discharge machining or the like, there is a problem that the processing time of the sleeve 62 becomes longer and the practicality and mass productivity are poor due to an increase in machining cost. It was.
[0012]
The present invention solves such a conventional problem, eliminates the influence of air bubbles mixed in the bearing in the assembly process of the hydrodynamic bearing, and can be manufactured at low cost, and a spindle motor equipped with the hydrodynamic bearing. It aims at realizing.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problems, the hydrodynamic bearing of the present invention has an annular recess formed in a portion larger than the shaft shaft diameter on the sleeve surface facing the thrust plate that supports the load in the thrust direction, and the annular recess provided in the sleeve. Has a step or taper in the axial direction.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
(Embodiment 1)
FIG. 1 shows a hydrodynamic bearing according to a first embodiment of the present invention.
[0016]
In FIG. 1, a shaft 1 is inserted into a sleeve 2, a thrust plate 3 is fixed to the sleeve 2, and a dynamic pressure generating groove 4 a is formed in the shaft 1. Lubricating oil 5 is filled inside the hydrodynamic bearing, and an annular concave portion 7 is provided on the surface of the sleeve 2 facing the thrust plate 3. A step portion 9 is formed in the axial direction at a portion larger than the shaft diameter of the concave portion 7. It is comprised so that it may provide.
[0017]
The dynamic pressure bearing configured as described above supports a radial load by dynamic pressure generated by the dynamic pressure generating groove 4a formed on the shaft 1 when the motor is driven, and the shaft end SR surface and the thrust plate 3 are pointed. A thrust bearing that is configured in contact with it supports the load in the thrust direction.
[0018]
When assembling the hydrodynamic bearing as shown in FIG. 1, the shaft 1 is inserted into the sleeve 2. In the hydrodynamic bearing assembly process, there are a case where the shaft 1 is inserted into the sleeve 2 where the thrust plate 3 is already fixed, and a case where the thrust plate 3 is fixed after the shaft 1 is inserted into the sleeve 2. In both cases, when the shaft 1 is inserted into the sleeve 2, the lubricating oil 5 is applied on the outer peripheral surface of the shaft 1 or the inner peripheral surface of the sleeve 2, and the lubricating oil 5 absorbs air when the shaft 1 is inserted. There is a risk of biting.
[0019]
The air entrained in the bearing together with the lubricating oil 5 when the shaft 1 is inserted is pushed into a recess 7 provided in the inner peripheral portion of the sleeve 2 and is partitioned by a step portion 9 formed at a portion larger than the shaft diameter. Enter the part that is. By configuring the air bubbles 6 to be confined in the concave portions 7 partitioned by the stepped portion 9, it can act as an expected hydrodynamic bearing.
[0020]
Accordingly, it is possible to prevent the bubbles 6 from entering the radial bearing formed by the side surface of the shaft 1 and the inner peripheral surface of the sleeve 2, and the bubbles 6 from being caught in the dynamic pressure generating groove 4a. Such as tilt and shaft runout can be prevented. Further, since it is possible to prevent the bubbles 6 from entering the thrust bearing formed by the end SR surface of the shaft 1 and the thrust plate 3, the bubbles 6 can be prevented from biting into the point contact portion between the shaft 1 and the thrust plate 3. It is possible to prevent problems such as seizure of the point contact portion due to the shortage, acceleration of wear of the thrust bearing portion, acceleration of thermal deterioration of the lubricating oil 5, and the life of the bearing portion can be extended.
[0021]
In the present embodiment, the dynamic pressure generating groove is formed on the side surface of the shaft, but the same effect can be obtained even when the dynamic pressure generating groove is formed on the inner peripheral surface of the sleeve facing the side surface of the shaft.
[0022]
(Embodiment 2)
FIG. 2 shows a hydrodynamic bearing according to a second embodiment of the present invention.
[0023]
In FIG. 2, the shaft 11 is inserted into the sleeve 12, and the thrust plate 13 is fixed to the sleeve 12. A dynamic pressure generating groove 14 a is formed on the shaft 11, and a dynamic pressure generating groove 14 b is formed on a portion of the thrust plate 13 facing the end surface of the shaft 11. Lubricating oil 15 is filled inside the hydrodynamic bearing, and an annular recess 17 is provided on the surface of the sleeve 12 facing the thrust plate 13. A stepped portion 19 is formed in the axial direction at a portion larger than the shaft diameter of the recess 17. It is comprised so that it may provide.
[0024]
The dynamic pressure bearing configured as described above supports a load in the radial direction by the dynamic pressure generated by the dynamic pressure generation groove 14a formed on the shaft 11 when the motor is driven, and the dynamic pressure generation groove formed on the thrust plate 13. The load in the thrust direction is supported by the dynamic pressure generated by 14b.
[0025]
Also in this embodiment, as described above, when assembling the hydrodynamic bearing, there is a possibility that the lubricating oil 5 may get in the air when the shaft 11 is inserted, but there is a bubble in the recess 17 partitioned by the step portion 19. By configuring so that 16 can be enclosed, it can act as an expected hydrodynamic bearing. Therefore, the motor can prevent problems such as uneven rotation, shaft inclination, and shaft runout due to insufficient radial bearing rigidity, and can extend the life of the bearing portion.
[0026]
In this embodiment, the dynamic pressure generating groove 14a is formed on the side surface of the shaft and the dynamic pressure generating groove 14b is formed on the thrust plate. However, the dynamic pressure is generated on the inner peripheral surface of the sleeve facing the side surface of the shaft. The same effect can be obtained when the generation groove 14a is formed and the dynamic pressure generation groove 14b is formed on the end surface of the shaft 11 facing the thrust plate 13.
[0027]
(Embodiment 3)
FIG. 3 shows a hydrodynamic bearing according to a third embodiment of the present invention.
[0028]
In FIG. 3, the shaft 1 is inserted into the sleeve 22, the thrust plate 3 is fixed to the sleeve 22, and the dynamic pressure generating groove 4 a is formed in the shaft 1. Lubricating oil 25 is filled inside the hydrodynamic bearing, and an annular recess 27 is provided on the surface of the sleeve 22 facing the thrust plate 3. A tapered portion 29 is axially provided at a portion larger than the shaft diameter of the recess 27. It is comprised so that it may provide.
[0029]
The dynamic pressure bearing configured as described above supports a radial load by dynamic pressure generated by the dynamic pressure generating groove 4a formed on the shaft 1 when the motor is driven, and the shaft end SR surface and the thrust plate 3 are pointed. A thrust bearing that is configured in contact with it supports the load in the thrust direction.
[0030]
Also in this embodiment, as described above, when assembling the hydrodynamic bearing, there is a possibility that the lubricating oil 25 may get in the air when the shaft 1 is inserted, but there are bubbles in the recesses 27 partitioned by the tapered portion 29. By configuring so that 26 is confined, it can act as an expected hydrodynamic bearing. Therefore, the motor can prevent problems such as uneven rotation, shaft inclination, and shaft runout due to insufficient radial bearing rigidity, and can extend the life of the bearing portion.
[0031]
(Embodiment 4)
FIG. 4 shows a hydrodynamic bearing according to a fourth embodiment of the present invention.
[0032]
In FIG. 4, the shaft 11 is inserted into the sleeve 32, and the thrust plate 13 is fixed to the sleeve 32. A dynamic pressure generating groove 14 a is formed on the shaft 11, and a dynamic pressure generating groove 14 b is formed on a portion of the thrust plate 13 facing the end surface of the shaft 11. Lubricating oil 35 is filled inside the hydrodynamic bearing, and an annular recess 37 is provided on the surface of the sleeve 32 facing the thrust plate 13. A tapered portion 39 is axially provided at a portion larger than the shaft diameter of the recess 37. It is comprised so that it may provide.
[0033]
The dynamic pressure bearing configured as described above supports a load in the radial direction by the dynamic pressure generated by the dynamic pressure generation groove 14a formed on the shaft 11 when the motor is driven, and the dynamic pressure generation groove formed on the thrust plate 13. The load in the thrust direction is supported by the dynamic pressure generated by 14b.
[0034]
Also in this embodiment, as described above, when assembling the hydrodynamic bearing, there is a possibility that the lubricating oil 35 may get in the air when the shaft 11 is inserted, but there is a bubble in the concave portion 37 partitioned by the tapered portion 39. By configuring so as to confine 36, it can act as an expected hydrodynamic bearing. Therefore, the motor can prevent problems such as uneven rotation, shaft inclination, and shaft runout due to insufficient radial bearing rigidity, and can extend the life of the bearing portion.
[0035]
(Embodiment 5)
FIG. 5 shows a spindle motor equipped with a hydrodynamic bearing according to the first embodiment of the present invention. FIG. 5 is a sectional view thereof.
[0036]
In FIG. 5, a stator 41 having a stator coil that generates a magnetic field in an excited state is included, and a rotor having a rotor magnet 42 that obtains a rotational force by electromagnetic interaction with the magnetic field of the stator coil is included. A shaft 1 for supporting and a sleeve 2 for supporting the shaft 1 are provided. A dynamic pressure generating groove 4a is formed on the side surface of the shaft 1 to constitute a sleeve 2 and a radial bearing facing each other. The thrust plate 3 is fixed to the sleeve 2 and constitutes a thrust bearing by making point contact with the shaft end SR surface facing the thrust plate 3. An annular recess 7 is provided on the surface of the sleeve 2 facing the thrust plate 3, and a step 9 is provided in the axial direction at a portion larger than the shaft diameter of the recess 7. Lubricating oil 5 is filled inside the hydrodynamic bearing, but when the shaft 1 is inserted into the sleeve 2 in the hydrodynamic bearing assembly process, the lubricating oil 5 entraps air and causes bubbles 6 to intervene inside the bearing. ing.
[0037]
When the stepped portion 9 is provided in the annular recess 7 of the sleeve 2 in this way, it is possible to confine the air bubbles 6 that are entrained in the bearing together with air in the bearing 7 in the recess 7 by the stepped portion 9. Become. Accordingly, it is possible to prevent the bubbles 6 from entering the radial bearing formed by the side surface of the shaft 1 and the inner peripheral surface of the sleeve 2, and the bubbles 6 from being caught in the dynamic pressure generating groove 4a. Such as tilt and shaft runout can be prevented. Further, since it is possible to prevent the bubbles 6 from entering the thrust bearing formed by the end SR surface of the shaft 1 and the thrust plate 3, the bubbles 6 can be prevented from biting into the point contact portion between the shaft 1 and the thrust plate 3. It is possible to prevent problems such as seizure of the point contact portion due to the shortage, acceleration of wear of the thrust bearing portion, and acceleration of thermal deterioration of the lubricating oil 5, thereby extending the life of the motor.
[0038]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various application developments are possible within the scope of the present invention.
[0039]
【The invention's effect】
As described above, in the hydrodynamic bearing according to the present invention, even when air is mixed into the bearing during the hydrodynamic bearing assembly process, air bubbles present inside the bearing are prevented from entering the hydrodynamic pressure generation site. As a result, the pressure increase in the dynamic pressure generating portion proceeds smoothly and the expected bearing rigidity can be obtained. In addition, problems such as uneven rotation, insufficient flying height, shaft inclination, shaft runout due to insufficient bearing rigidity, bearing seizure, accelerated wear, and accelerated deterioration of the lubricating oil due to insufficient lubricating oil can be prevented.
[0040]
Further, since such a dynamic pressure bearing is mounted, an excellent spindle motor which is free from problems such as uneven rotation, insufficient flying height, shaft inclination, shaft runout, etc., and which is inexpensive and has a long life can be realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a hydrodynamic bearing according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a hydrodynamic bearing according to another embodiment of the present invention. FIG. 4 is a sectional view of a hydrodynamic bearing according to still another embodiment of the present invention. FIG. 5 is a sectional view of a spindle motor equipped with the hydrodynamic bearing according to an embodiment of the present invention. Cross section of a conventional dynamic pressure bearing [Fig. 7] Cross section of a spindle motor equipped with a conventional dynamic pressure bearing [Explanation of symbols]
1, 11, 51, 61 Shaft 2, 12, 22, 32, 52, 62 Sleeve 3, 13, 53 Thrust plate 4a, 4b, 14a, 14b, 54a Dynamic pressure generating groove 5, 15, 25, 35, 55 Lubrication Oil 6, 16, 26, 36, 56 Air bubbles 7, 17, 27, 37, 57, 67 Recess 9, 19 Step 29, 39 Taper 41 Stator 42 Rotor magnet 68 Air vent hole

Claims (3)

The axis,
A sleeve that fits with the shaft and supports a radial load;
A thrust plate fitted to the sleeve so as to be perpendicular to the shaft and supporting a load in a thrust direction ;
An annular recess is formed in a portion of the sleeve that faces the surface of the thrust plate and is larger than the outer diameter of the shaft ,
The space constituted by the shaft, the thrust plate, and the annular recess is a sealed space, and the thrust plate and the sleeve are not in contact with each other at the innermost peripheral portion of the recess,
Has a tapered portion where the distance from the thrust plate is increased toward the outer periphery from the inner periphery to the recess, the tip portion of the tapered portion is the position of the outermost and innermost of the recess,
By filling the sealed space with a lubricant ,
A hydrodynamic bearing configured such that bubbles are confined in a tip portion of a tapered portion of the concave portion.   The dynamic pressure bearing according to claim 1, wherein a dynamic pressure generating groove is formed in the thrust plate. Having a stator with a stator coil that generates a magnetic field in an excited state;
Having a rotor with a rotor magnet that obtains rotational force by electromagnetic interaction with the magnetic field of this stator coil;
A spindle motor comprising a shaft and a sleeve for supporting the rotor, and a thrust plate, wherein the dynamic pressure bearing according to claim 1 is mounted on the shaft or the sleeve.

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